摘要:

The modification of nitrogen isotopic signals during particle sedimentation in the sea is of great interest for the use of sedimentary δ15N-values as a paleoceanographic tool. The effect of organic matter degradation on such modification was studied by analyzing nitrogen, hydrolyzable amino acids (THAA) and δ15N-values in a suit of marine settling particles collected from the Bay of Bengal, Indian Ocean, by using time-series sediment traps, and in underlying sediments. The flux of settling particles showed temporal variations which are related to the monsoons, the major climatic feature of this marine region. During high flux periods settling particles are enriched in nitrogenous material that is less degraded and exhibit higher δ15N-values than particles showing characteristics of degradation. At the sediment surface more than 95% of the settling particulate nitrogen is lost and the δ15N-values of the residual sedimentary nitrogen are higher than those of settling particles. The observed increase is interpreted to be due to fractionation during degradation of organic matter.

ISSN:1025-6016    

DOI:10.1080/10256019708036346

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1025-6016    

DOI:10.1080/10256019708036347

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Breath tests using13C-labelled substrates require the measurement of13CO2/12CO2ratio in breath gas samples. Next to isotope ratio mass spectrometry (IRMS), which is very sensitive but also complex and expensive, alternatively isotope selective nondispersive infrared spectrometry (NDIRS) can be used to determine the13CO2/12CO2ratio in expired breath. In this study we compared NDIRS- with IRMS-results to investigate whether the less expensive and very simply to operate NDIRS works as reliable as IRMS. For this purpose we applicated 1-13C-Phenylalanine to patients with advanced liver cirrhosis and healthy volunteers and took duplicated breath samples for IRMS and NDIRS at selected time points. Our data show a good correlation between these two methods for a small number of samples as required for simple breath tests. Longer series, where repeated measurements are required on the NDIRS instrument lead to a decreasing correlation. This indicates the superiority of IRMS concerning13CO2-kinetics over longer time periods.

ISSN:1025-6016    

DOI:10.1080/10256019708036348

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1025-6016    

DOI:10.1080/10256019708036349

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:1025-6016    

DOI:10.1080/10256019708036325

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor